Moss Melt Concentrate, a moss and algae herbicide from Green Spear Inc., has recently received EPA registration for use on roofs, lawns, turf, and outdoor surfaces and structures. The active ingredient is an emulsified d-Limonene, which acts as a natural degreaser. It strips away the waxy surface of moss and algae without direct sunlight or warm temperatures. The product is rain-fast within one hour. Moss Melt will not stain concrete, brick, pavement, stucco or wood and will not damage gutters, metal flashing or downspouts. One gallon kills up to a 12,500-square-foot area. The product currently is available in the Pacific Northwest.